[Boatanchors] 1625 tube

[Gary Schafer]

Vic Rosenthal wrote:
> Glen Zook wrote:
> 
>> The 1625 is the 7-pin "medium" base and not octal.
> 
> 
> More 1625 trivia: one other difference between the 1625 and 807 that 
> should be noted is that the 1625 has its supressor grid internally 
> connected to the cathode, whereas it goes to one of the base pins in the 
> 807.  This means that you cannot use an unmodified 1625 in a gg amplifier.
> 
> To get really trivial, some brands of 1625 (which? -- now we have gone 
> past the point at which even my knowledge of trivia is exhausted) had 
> this connection made in the base.  So you could drill a small hole in 
> the side of the base of these, heat the pin with a soldering iron, and 
> stick a needle-nose plier in the hole to lift the wire from the 
> suppressor and move it to another pin!
> 
> It sounds silly, but since 1625's were essentially free in the '50's and 
> early '60's many people did it.
> 

None of the RCA brand could be modified if I remember right. We used to 
order 1625's from Fair radio and specify National Union, Sylvania and 
another brand that I can't remember. I always cut a slot in the lower 
part of the base to modify them. Sometimes you needed more room as they 
sometimes had the suppresser wire and cathode wire twisted together.
Some people heated the base to loosen the glue and removed the whole base.

I melted many screens and grids in those tubes running them in grounded 
grid. Of course I ran them at much more than 100 watts per pair.

A Central electronics 20A driving pair of 1625's in GG to drive a pair 
of 813's in GG was not uncommon. Although the 20A was a little short on 
drive for the 1625's it did work pretty well and was simple. The guys 
that did not want to bother with modifying 1625's would use 837's which 
cost a little more.

Putting 4 of them in an old command set chassis for an amp was kind of 
popular. Use the two existing sockets and add 2 more on standoffs to get 
them well below the chassis.

73
Gary  K4FMX